A method of manufacturing sealing strips for pistons of rotary piston machines is known (German Offenlegungschrift No. 1,601,836) in which the sealing strip is cut from a length of metal strip, then bent to the desired radius of curvature and, subsequently, has a hard layer applied to its running surface. In another known method (German Offenlegungschrift No. 1,601,836) a metal band or strip is formed into a helical coil, then cut off in the longitudinal direction; and the sealing strips formed thereby are provided on their running surfaces with a hard layer. The hand treatment of the individual sealing strips of relatively small cross section which is necessary in these processes is however of appreciable difficulty. Moreover in the application of a hard layer, for example a layer of chromium, it has been found that thicker layers are formed at both ends, and also the material of the layer builds up unevenly at the corners of the side faces. The subsequent work which is required on the individual sealing strips to obtain a usable running surface, and which is performed in special machines involves, however, a high cost and furthermore leads to a relatively high proportion of rejects. In a further known process (German Offenlegungschrift No. 2,349,516) it is proposed instead to cut a metal band up into strips and then coat the sealing strips on their running surfaces in packets and only then bring them to their arcuate shape and cut them to length. In this process likewise one cannot avoid the formation of thicker layers at the ends of the strips; it is true, that these layers are removed on cutting to length but this leads to the requirement that each sealing strip must have a correspondingly greater initial length. Moreover, in this process again, the hand work required on the individual thin sealing strips cannot be avoided; and so, quite apart from the sources of faults which this gives rise to, efficient and commercially practical production is not to be achieved in this way.